It depends on the stain. If it is a water base stain then no. If it is a oil or solvent base it should be fine.
Yes, make sure the stain is completely dry and you should have no difficulty.
try maybe home depot or Lowe's
All of it. Otherwise the latex stain will seal the surface of the wood and the oil will not be able to penetrate into the wood. Sanding won't remove all of the residue. You'll want to use a paint stripper/stain remover too.
You should never paint a deck, the paint will peel (unless you live in a very arid climate I guess. The deck may be stained, you can put either oil or latex stain over old oil stain.
It depends on the stain. If it is a water base stain then no. If it is a oil or solvent base it should be fine.
Yes, make sure the stain is completely dry and you should have no difficulty.
yes
Yes you can if it is a solid stain. However, if you're using toners or semi-transparent stains, you'll want to remove all the water based product prior to applying the oil based stain, otherwise, it will appear blotchy if the water based stain is worn unevenly.
try maybe home depot or Lowe's
All of it. Otherwise the latex stain will seal the surface of the wood and the oil will not be able to penetrate into the wood. Sanding won't remove all of the residue. You'll want to use a paint stripper/stain remover too.
You should never paint a deck, the paint will peel (unless you live in a very arid climate I guess. The deck may be stained, you can put either oil or latex stain over old oil stain.
Sometimes hard water will evaporate after soaking in, leaving the minerals behind, looks like a stain. And some blacks can etch with different pH level liquids or foods. Oil can sometimes soak in as well. And the UV in sunlight can lighten some stones.
No, oil needs to penetrate the surface and the latex stain will inhibit that penetration.
Yes, but why waste the varnish. - (it is meant for bare wood )
No it does not.
There are hundreds of shades of stain in all kinds of medium. I personally prefer gel stain as I find it easy to work with. Other people use liquid stains in water base or oil base.